Frequency multiplier



Jan. 5, 1960 H. HAVSTAD 2,920,286

FREQUENCY MULTIPLIER Filed Sept. 6; 1955 3 Sheets-Sheet 1 INVENTOR HARALO HA VSTAD AGENT Jan. 5, 1960 H. HAVSTAD 2,920,286

FREQUENCY MULTIPLIER Filed Sept. 6, 1955 3 Sheets-Sheet 2 INVENTOR HARALD HA VSTAD AGENT H. HAVSTAD FREQUENCY MULTIPLIER 3 Sheets-Sheet 3 INVENTOR HARALD HA VSTAD BY flyJJc/W AGENT United States Patent FREQUENCY MULTIPLIER Harald Havstad, Allendale, N.J., assignor to International Telephone and Telegraph Corporation, Nutley, N.J., a corporation of Maryland Application September 6, 1955,'Serial No. 532,720

18 Claims. c1. an-'53 This invention relates to frequency multipliers and more particularly to an improved frequency multiplier for operation in the frequency range above 30 megacycles.

When very high frequency stability is required in frequency ranges above 30 megacycles, such as the UHF frequency range, the commonly employed system involves multiplying the frequencies obtained from a crystal control oscillator of high stability by means of a chain or series of vacuum tube multipliers and amplifiers. These multiplier stages usually employ resonant elements at the input and output of the stages with matching elements employed between stages. When the frequencies to be multiplied are above relatively high frequency, say about 300 megacycles, the resonant elements usually become some sort of transmission line or cavity, and, for the case where the multiplying factor exceeds 6, a large nun:- ber of cavities and matching networks are necessary.

Generally, the adjustment of resonance in the resonant element, such as the transmission line cavities, and the location of excitation of these resonant elements produce symmetrical modes of operation therein. In the case of transmission line cavities and in particular radial transmission line cavities the tuning is accomplished at the center of the cavity or the radius of the cavity is adjusted by means of shorts across the cavity. These tuning elements and the central excitation of the cavities produce symmetrical field configuration therein.

An object of this invention is to provide an improved frequency multiplier wherein the number of resonant elements is substantially half of the usual number found in .such prior art arrangements.

Another object of this invention is to provide a frequency multiplier employing transmission line cavity resonant elements having nonsymmetrical modes of operation therein to' obtain frequency multiplication with a substantial reduction in the number of resonant elements in comparison with the prior art arrangements for frequency multiplication by the same factor.

Still another object of this invention is to provide a frequency multiplier employing a plurality of series connected transmission line cavities resonant at harmonically related frequencies and electrically coupled by means of non-linear elements disposed in the non-symmetrical electromagnetic fields excited in said cavities to obtain "the electromagnetic field for removing a signal therefrom whose frequency is harmonically related to the frequency of the input signal.

Another feature of this invention is the provision of at least two resonant cavities each being symmetrically disposed about a different central axis and each being resonant at a harmonic of the frequency of an input signal.

2,920,286 Patented Jan. 5, 1960 Each cavity includes an input means disposed within the cavity walls and in spaced relation to the respective central axis, the input means exciting an electromagnetic field within the cavity which is non-symmetrically related to their respective central axes, and an output means disposed at a given point in the electromagnetic field of each cavity for coupling a signal therefrom whose frequency is harmonically related to the frequency of the input signal, the output means and the input means of adjacent ones of the cavities being an integral part of a single component, said signal component connecting said cavities in a series or tandem relationship.

The above-mentioned and other features and objects of this invention will become more apparent by reference to thefollowing description taken in conjunction with the accompanying drawings, in which:

Fig. 1 is a cross-sectional view of the frequency multiplier of this invention;

Fig. 2 is a cross-sectional view taken along line 22 of Fig. 1; and

Fig. 3 is an equivalent electrical circuit diagram of the structure illustrated in Fig. 1.

Referring to Figs. 1 and 2, there is illustrated therein a plurality of resonant cavities including cavities 1, 2, 3 and 4 in cooperative association with non-linear devices such as electron discharge devices 5, 6, 7, and 8 of the planar electrode type for frequency multiplication. Each of the plurality of cavities employ substantially the same general structural organization with the difference between being in the physical size of the cavities. This difference of physical size of the cavities is a consequence of the increasing frequency of the signals passing therethrough.

With particular reference to cavity 1, the resonant structure is shown to comprise a cylindrical or annular wall 9 disposed coaxially about a central or longitudinal axis 10. The bottom of cylinder 9 is closed by means of plate 11 andtop of cylinder '9 is closed by a portion of plate 12. Plates 11 and 12 each include a' pair of openings therethrough spaced from central axis 10. The apertures "13 and 14 of plate 11 are aligned with apertures 15 and 16 of plate 12', respectively, to coperate in the reception of electron discharge devices 5 and 6 therein as illustrated in Fig. 1.

An area of plate 12 surrounding aperture 13 has disposed in overlying relationship therewith a dielectric member 17 which is sandwiched between annular member 18 and plate '12. Member 18 includes contact fingers 19 for electrical contact with the anode contacting surface 20. A B+. voltage'is coupled to the anode of device 5 by means of anode contacting surface 20, contact fingers 19, member 18 and terminal 21. This structural organization places the anode of device *5 at a sufficient potential above ground to provide an amplification of a signal applied to the cathode of device -5 through cathode contacting surface 22. The plate 11 incorporates at aperture 14 a contacting assembly 23 to provide electrical continuity between the grid of device '5 through grid contacting surface 24 and the walls of cavity 1. This places the grid and cavity walls at thesame D.C. potential which in this instance is ground.

Thus, discharge device 5 is employed in a grounded grid type operation for amplification of a signal applied to the cathode thereof. Through the cooperation of the electron discharge devices 5 and 6 and resonant'cavity 1, the signal applied to the cathode contacting surface 22 is amplified and frequency multiplied, the dimensions of cavity 1 being such as to produce a frequency therein harmonically related to the frequency of the signal applied at input terminal 25.

The signal applied'at input terminal 25 is coupled to the cathode contacting surface 22 by means of choke 26 which is employed to isolate the RF signal from the source of filament voltage applied at terminal 27.

Device 6 is positioned in cavity 1 to place the control gr'id thereof in contact with the Walls of cavity 1, plate 12, by, means of the gridicontact member 28 associated therewith. The cathode of device -6 is disposed in an electrically isolated condition with respect to plate 11 by means of dielectric 29 and plate 30 which has coupled thereto the necessary D.C. potentials for the operation of the tube as a whole and the'filaments in particular. This structural arrangement places the electrode space between the control grid and the cathode of device 6 across the cavity 1 in a coupling relation with the nonsymmetrical electromagnetic field excited in the cavity by'the interelectrode spacebetween the control grid and the anode of device 5. The energy intercepted by the electrode space between-control grid and cathode of device 6 is electronically coupled to the electrode space I anode of electron discharge device 5, DC. potential from a 'B+ source is coupled through annulis 34 and contact 35 to the anode contacting surface 36 of device 6. This electrical conducting path is insulated from the grounded cavity wall by means of dielectric 37.

As in the case with cavity 1, the electrode space between the cathode and control-grid of device 7 intercepts and extracts from the non-symmetrical electromagnetic field energy which is harmonically related to the energy injected in the cavity. This energy is electron coupled within device 7 for excitation 'of a non-symmetrical electromagnetic field in cavity 3. The structural configuration for this tube 7 is substantially identical with the structure detailed in connection with tubes 5 and 6. This process of driving one cavity with the anode-control grid electrode space and "extracting a harmonically related signal from this cavity with the cathode-control grid electrode space of another tube which electronically couples this extracted signal to the anode-control grid electrode spacethereof for excitation of the next adjacent cavity may be continued in as many steps as necessary to achieve the desired multiplication of the frequency of the signal injected in the first cavity. The operating conditions of the tubes may be adjusted by the proper application of anode and cathode voltages thereto to achieve the desired amplification of the signal passing therethrough.

Each of the radial tranmission line cavities of Fig. 1 includes a tuning means in a spaced relation with the central axis thereof to provide the desired tuning range for the cavities. I These tuning means are illustrated by capacitive tuning adjustments 38, 39, 40 and 41. The signal at the last cavity is illustrated as being coupled therefrom by means of adjustable loop couplings 42 and 43. The loop coupling 43 includes therein adiode detector which enables the obtaining of an indication of the amplification achieved in the cavity structure; The loop coupling 42 would be utilized to couplethe amplified and multiplied signal to further circuits such as radio frequency transmitting equipment for, radiation thereof from a suitable antenna. i

In the previous discussion it has been stated that the operationiof, the frequency multiplier of this invention dependsfupon 'the'spaced relation between the electron discharge devices and tuning means and the central axis of the cavities to eliminate the heretofore employed intermediate cavities. Referring to Fig. 2, it will be. noted c r a u 4 7 that the discharge devices 5 and 6 and the capacitive tuner 38 are in aligned relationship along the transverse axis of the cylinder 9. I V

Cavity 1 also includes a capacitive tuner 44 which is employed to cooperate in the matching of the signal applied at terminal'25 to the impedance of the electrode space between the control grid and the cathode of device 5.

Radial transmission type cavities have been applied in the frequency multiplier of this inventionsince the shapes of the cavities can be cheaply formed from ordinary commercial brass tubing and flat commercial brass sheet. Sufliciently good match is achieved and no slug tuners or other impedance matching networks need be employed between cavities or in the RF output coupled from output connection 42 in a frequency range of 400 megacycles to 2,000 megacycles.

Referring to Fig. 3, an equivalent electricalcircuit of Figfl is disclosed wherein corresponding components are indicated by a primed reference character. The 'heavy'lines of Fig. 3 are the walls of the cavities l, 2, 3 and 4 of Fig. l and indicated in Fig. 3 as 1', 2, 3' and 4'. In the operation of the structure of Fig. 1, a crystal controlled frequency oscillator 45 is employed to develop a signal for application to the cathode 46 of device 5'. This will apply an input signal in the electrode space between cathode 46 and grid 47; Filament heating potential is applied from terminals 48 through the RF. choke 26 to the filament 49. A similar arrangementas indicated is employed in connection with the other discharge devices of the circuit. The anode potential applied to each of the discharge devices is isolated electrically from the walls of the cavities by the capacitorformed by the dielectric material disposed between the cavity walls and the potential applying member. This is structurally illustrated in Fig. 1 by plate i 12, member 18 and dielectric material 17, and sche- Such a structural capacitor is illustrated in Fig. l as ineluding plate 11, plate 30 and the dielectric material 29 therebetween. This is schematically shown in Fig. 3 by capacitors 51. Fig. 3 illustrates schematically the capacitive tuning slugs by means of the variable condensers 52 connected across the walls of each cavity. The'input matching or tuning slug 44 of Fig. 1 is depicted by the variable condenser 53 in the circuit of Fig. 3.

' The arrangement herein disclosed provides'a frequency multiplier which is relatively inexpensiveto manufacture and provides sufficiently good impedance matching between cavities to eliminate tuners or other impedance matching networks between cavities and at the RF. out put of the frequency multiplier. Thus, the number of cavities employed is reduced from the number employed in prior art arrangements to about one half.

While I have described above the principles of my invention in connection With specific apparatus, it is to be clearly understood that this description is made only by Way of example and not as a limitation to the scope of my invention as set forth in the objects thereof and the accompanying claims.

-I claim:

l. A frequency multiplier comprising a source of signals having a given frequency, a resonant cavity symmetrically disposed about a central axis, said cavity being resonant at a given harmonic of said given frequency,

a non-linear input means disposed within said'cavity and in a'spaced relation to said central axis, said input means coupling signals from said source to excite an electromagnetic field within said cavity non-symmetrically reaoaqsse lated to said central axis, and a non-linear output means disposed at a given point in said electromagnetic field for coupling a signal from said cavity whose frequency is harmonically related to said given frequency.

2. A frequency multiplier comprising a source of signals having a given frequency, a resonant cavity symmetrically disposed about a central axis, said cavity being resonant at a given harmonic of said given frequency, a first planar electrode type election discharge device disposed in a spaced relation to said central axis, said first device having an input electrode space and an output electrode space in electron coupled relationship, the output electrode space of said first device being disposed within said cavity, means coupling the signals of said source to the input electrode space of said first device, the output electrode space of said first device exciting an electromagneticfield within said cavity with the signals of said source, said electromagnetic field being non-symmetrically related to said central axis, a second planar electrode type electron discharge device having an input electrode space and an output electrode space in electron coupled relation ship,'the input electrode space of said second device being disposed at a given point in said electromagnetic field, and means for coupling from the output electrode space of said second device a signal Whose frequency is harmonically related to said given frequency.

3. A frequency multiplier comprising a source of signals having a given frequency, a resonant cavity symmetrically disposed about a central axis, said cavity being resonant at a given harmonic of said given frequency, a direct current reference potential, means coupling said cavity to said reference potential, a first electron discharge device disposed in a spaced relation to said central axis, said first device having a cathode, an anode and a control grid, means directly coupling the control grid of said first device to a wall of said cavity, means capacitively coupling the anode of said first device to the opposite wall of said cavity to dispose the electrode space between the anode and the control grid of said first device within said cavity, means coupling the signals of said source to the electrode space between the cathode and the control grid of said first device, electron beam means coupling the signal of said source from the last mentioned electrode space to the first mentioned electrode space for exciting an electromagnetic field within said cavity, said electromagnetic field being non-symmetrically related to said central axis, a second electron discharge device having a cathode, an anode and a control grid, means directly coupling the control grid of said second device to a wall of said cavity, means capacitively coupling the cathode of said second device to the opposite wall of said cavity to dispose the electrode space between the cathode and the control grid of said second device within said cavity at a given point in said electromagnetic field, electron beam means coupling the signal of the electrode space between the cathode and the control grid of said second device to the electrode space between the control grid and the anode of said second device, and means coupled to the last mentioned electrode space for coupling therefrom a signal Whose frequency is harmonically related to said given frequency.

4. A frequency multiplier comprising a source of signals having a given frequency, a resonant cavity, tuning means disposed in said cavity to tune said cavity for resonancev at a given harmonic of said given frequency, a non-linear input means for coupling the signals of said source to said cavity, said non-linear means being disposed in the electromagnetic field of said cavity, and non-linear output means disposed in the electromagntic field of said cavity for coupling a signal therefrom whose frequency is harmonically related to said given frequency.

5. A frequency multiplier comprising a source of signals having a given frequency, a resonant cavity symmetrically disposed about a central axis, means disposed within said cavity in spaced relation to said central axis to tune said cavity for resonance at a given harmonic of said given frequency, an input means disposed Within said cavity and in a spaced relation to said central axis, said input means coupling signals from said source to excite an electromagnetic field within said cavity non-symmetrically related to said central axis, and an output means disposed at a given point in said electromagnetic field for coupling a signal from said cavity whose frequency is harmonically related to said givenfrequency.

6. A frequency multiplier comprising a source of signals having a given frequency, a resonant cavity symmetrically disposed about a central axis, capacitive tuning means disposed within said cavity in spaced relation to said central axis to tune said cavity for resonance at a given harmonic of said given frequency, an input means disposed Within said cavity and in a spaced relation to said central axis, said input means coupling signals from said source to excite an electromagnetic field within said cavity non-symmetrically related to said central axis, and an output means disposed at a given point in said electromagnetic field for coupling a signal from said cavity whose frequency is harmonically related to said given frequency.

- 7. A frequency multiplier comprising a source of signals having a given frequency, a radial transmission line cavity resonant at a given harmonic of said given frequency symmetrically disposed about a central axis, a non-linear input means for coupling the signals of said source to said cavity disposed in spaced relation from said centeral axis to excite an electromagnetic field within said cavity non-symmetrically related to said central axis and a non-linear output means disposed in spaced relation from said central axis and in the electromagnetic field of said cavity for coupling a signal therefrom whose frequency is harmonically related to said given frequency.

8. A frequency multiplier comprising a source of signals having a given frequency, a first and second resonant cavity each symmetrically disposed about a difierent central axis, each of said cavities being resonant at a harmonic of said given frequency, an input means disposed within each of said cavities and in spaced relation to the respective central axis of said cavities, said input means exciting an electromagnetic field within said cavities non-symmetrically related to their respective central axes, an output means disposed at 'a given point in the electromagnetic field of each of said cavities for coupling a signal from the respective ones of said cavities whose frequency is harmonically related to said given frequency, the output means of said first cavity and the input means of said second cavity being an integral part of a single component, means coupling the signals of said source to the input means of said first cavity, and means coupling the frequency multiplied signal from the output means of said second cavity.

9. A frequency multiplier comprising a source of signals having a given frequency, a first and second resonant cavity each symmetrically disposed about a different central axis, each of said cavities including means to tune said cavity for resonance at a harmonic of said given frequency, an input means disposed within each of said cavities and in spaced relation to the respective central axis of said cavities, said input means exciting an electromagnetic field within said cavities non-symmetrically related to their respective central axes, an output means disposed at a given point in the electromagnetic field of each of said cavities for coupling a signal from the respective ones of said cavities whose frequency is harmonically related to said given frequency, the output means of said first cavity and the input means of said second cavity being an integral part of a single component, means coupling the signals of said source to the input means of said first cavity, and means coupling the frequency multiplied signal from the output means of said secod cavity.

10. A frequency multiplier comprising a source of signals having a given frequency, a first and second resonant cavity each symmetrically disposed about a diflerent cen- 7 tral axis, eachof said cavities including capacitive means disposed within said cavity contiguous opposite walls thereof for tuningsaidoavity to'resonance at a harmonic of said given frequency, an input means disposed within each of said cavities and in spaced relation to the respective central axis of said cavities, said input means exciting an electromagnetic field Within" said cavities nonsymmetrically related to their 'res'pectivelcentral' axes, an output means disposed at a'given point in the electro magnetic field of each of said cavities for coupling a signal from the respective ones of said'cavitics whose frequency is harmonically related to" said given. frequency, the output means of said first cavity and the input means of said second cavity being an integral part'of a single component, means coupling the signals of said source to the input means of said first cavity, and means coupling 'the frequency multiplied signal from the output means of said second cavity.

11. A frequency multiplier comprising a source of signals having a given frequency, a first and second resonant cavity each symmetrically disposed about' a diiferent cen tral axis, each of said cavities including capactive means disposed within said cavity in spaced relation to the respective one of said central axes and contiguous opposite walls of said cavity for tuning said cavity to resonance at a harmonic of said given frequency, an input means disposed Within each of saidcavities land in .spacedrelation to the respective central axis of said cavities, said input means excting an electromagnetic field within said cavities non-symmetrically related to their respective central axes, an output means disposed at a'given point in the electromagnetic field of each of said cavities for coupling a signal from the respective ones of said cavities whose frequency is harmonically related to saidgiven frequency the output means of said first cavity and the input means of said second cavity being an integral part of a single component, means coupling the s'ignals'of said source to the input means of said first cavity, and means coupling the frequency multiplied signal from the output means of said second cavity. i

12. A frequency multiplier comprising a source of signals having a given frequency, a first and second radial transmission line cavity each symmetrically disposed about a different central axis, each of said cavities'being resonant at a harmonic of said given frequency pan input means disposed within each of said cavities and in spaced relation to the respective central axis of said cavities, said input means exciting an'electromagneticfield within said cavities non-symmetrically related to their respective central axes,an output means disposed at a' given point in the electromagnetic field of each of said cavities for coupling a signal from the respective ones of said cavities whose frequency is harmonically related to said given 7 frequency, the output means of said first cavity and the input means of said second cavity being an integral part of a single component, means coupling the signals of said source to the input means of said first cavity, and means coupling the frequency multiplied signal from the output means of said second cavity.

13. A frequency multiplier comprising a source of signals having a given frequency, a first and second resonant cavity each symmetrically disposed about a different central axis, each of said cavities being resonant at a harmonic of said given frequency, a first electron discharge device having an input electrode space and an output electrode space in electron coupled relationship, said first device being disposed in spaced relation to the central axis of said first cavity with the output electrode space thereof being disposed within said first cavity for excitation of a non-symmetrical electromagnetic field therein with respect to the central axis ofsaid first cavity, an output means for said first cavity disposedat a given 'point in the electromagnetic field thereof for coupling a signal therefromv whose frequency is harmonically related to said given frequency, input means for said second cavity'disposed in spaced relation to the central axis thereof for excitation of anon-symmetrical electromagnetic field in said second cavitywith relation to the central axis thereof, a second electron discharge device having input electrode space and an output electrode space in electroncoupled relationship, the input electrode space of said second device being disposed in the electromagnetic field ofsaid second cavity for coupling a signal there from whose frequency is harmonically related to said given frequency, the output mean's of said first cavity and the input means of said second cavity including a third electron discharge device having an input electrode space and an output electrode space, input electrode space of said third device constituting the outputrneans of said first cavity and the output electrode space of said third device constituting the input means of said second cavity, means coupling the signals of said source to the input electrode space of said firstdevice and means coupling the frequency multiplied signals from the output electrode space of said second device. I

14. A frequency multiplier comprising a source of signals having a given frequency, a reference potential, a first and second resonant cavity each symmetrically disposed about a different central axis, each of said cavities being resonant at a harmonic of said given frequency, means coupling said cavities to said reference potential, a first electron discharge device having an input electrode space defined by the cathode and the control grid therein and an output electrode space defined by the anode and the control grid therein in electron coupled relationship, said first device being disposed in spaced relation to the central axis of said first cavity, meanscoupling the control grid of said first device to the walls of said first cavity, means coupling the anode of saidfirst device capacitively to the walls of said first cavity to dispose the output electrode space thereof within said 'first 'c'ant 'ror excitation of a non-symmetrical electromagnetic field therein with respect to the central axis of said first cavity, an output means for said first cavity disposed at a given point in the electromagnetic field thereof for coupling a signal therefrom Whose frequency is harmonically related to said given frequency, input means for said second cavity disposed in spaced relation to the central axis thereof for excitation of a non-symmetrical electromagnetic field in said second cavity with relation to the central axis thereof, a second electron discharge device having an input electrode space defined by the cathode and the control grid therein and an output electrode space de fined by the anode and the'control grid thereinin elec: tron coupled relationship, means coupling the' control grid of said second device to the walls of saidsecond cavity, means coupling the cathode of said second device capacitively to the Walls of said second cavity to dispose the input electrode space of said second device in the electromagnetic field of said second cavity for coupling a signal therefrom Whose frequency is harmonically re lated to said given frequency, the output means of said first cavity and the input means of said second cavity including a third electron discharge device having a cath ode, an anode and a control grid, means capacitively coupling the cathode of said third device to one wall of said first cavity, means coupling the control grid of said third device to the opposite wall of said first cavity and one wall of said second cavity, means coupling, the anode of said third device to the opposite wall of said second cavity, the electrode space between the cathode and the control grid of said third device constituting the output means of said first cavity and the electrode space between; the control grid and the anode of said third device constituting the input means of said second cavi'ty,'rneans coupling the signals of said source to the inputelectrode space of said first device and means couplingthe'fre quency multiplied signals from the output electrode space of said second device.

15. A frequency multipliercomprising a sourceof sig- 9 nals having a given frequency, a reference potential, a source of bias potential, a first and second resonant cavity each symmetrically disposed about a different central axis, each of said cavities being resonant at a harmonic of said given frequency, means coupling said cavities to said reference potential, a first electron discharge device having an input electrode space defined by the cathode and control grid therein and an output electrode space defined by the anode and the control grid therein in electron coupled relationship, means coupling the anode and the cathode of said. first device to said bias potential source to bias said first device for signal amplification, said first device being disposed in spaced relation to the central axis of said first cavity, means coupling the control grid of said first device to the walls of said first cavity, means coupling the anode of said first device capacitively to the walls of said first cavity to dispose the output electrode space thereof within said first cavity for excitation of a non-symmetrical electromagnetic field therein with respect to the central axis of said first cavity, an output means for said first cavity disposed at a given point in the electromagnetic field thereof for coupling an amplified signal therefrom whose frequency is harmonically related to said given frequency,-inp11t means for said second cavity disposed in spaced relation to the central axis thereof for excitation of a non-symmetrical electromagnetic field in said second cavity with relation to the central axis thereof, a second electron discharge device having an input electrode space defined by the cathode and the control grid therein and an output electrode space defined by the anode and the control grid therein in electron coupled relationship, means coupling the anode and cathode of said second device to said bias potential source to bias said second device for signal amplifications, means coupling the control grid of said second device to the walls of said second cavity, means coupling the cathode of said second device capacitively to the walls of said second cavity to dispose the input electrode space of said second device in the electromagnetic field of said second cavity for coupling an amplified signal therefrom whose frequency is harmonically related to said given frequency, the output means of said first cavity and the input means of said second cavity including a third electron discharge device having a cathode, an anode and a control grid, means capacitively coupling the cathode of said third device to one wall of said first cavity, means coupling the control grid of said third device to the opposite wall of said first cavity and one wall of said second cavity, means coupling the anode of said third device to the opposite wall of said second cavity, the electrode space between the cathode and the control grid of said third device constituting the output means of said first cavity and the electrode space between the control grid and the anode of said third device constituting the input means of said second cavity, means coupling the signals of said source to the input electrode space of said first device and means coupling the frequency multiplied and amplified signals from the output electrode space of said second device.

16. A frequency multiplier comprising a source of signals having a given frequency, a plurality of resonant cavities each symmetrically disposed about a different central axis, each of said cavities being resonant at a harmonic of said given frequency, an input means disposed within each of said cavities and in spaced relation to the respective central axis of said cavities, said input means exciting a non-symmetrical electromagnetic field therein with respect to the central axis of their respective central axes, an output means disposed at a given point in the electromagnetic field of each of said cavities for coupling a signal from the respective ones of said cavities whose frequency is harmonically related to said given frequency, the output means and input means of adjacent ones of said cavities being an integral part of a single component, said single component connecting said cavities in a tandem relationship, means coupling the signals of said source to the input means of the first of said cavities and means coupling the frequency multiplied signals from the output means of the last of said cavities.

17. A non-symmetrical cavity resonator comprising a cylindrical housing having an input means and an output means each disposed in a difierent radial location with respect to the axis of said housing, a first capacitance tuner and a second capacitance tuner, said first and second tuners being located at spaced points in said housing with one located closer to said axis than the other whereby said tuners determine the resonant frequency of said resonator and simultaneously match the impedance of said input means to the impedance of said output means.

18. A non-symmetrical cavity resonator comprising a cylindrical housing having an input means and an output means disposed in spaced relation on a diameter of said housing each of said means being offset from the axis of said housing, a first capacitance tuner and a second capacitance tuner, said first and second tuners being located at spaced points on said diameter with one located closer to said axis than the other whereby said tuners determine the resonant frequency of said resonator and simultaneously match the impedance of said input means to the impedance of said output means.

References Cited in the file of this patent UNITED STATES PATENTS 2,418,484 Samuel Apr. 8, 1947 FOREIGN PATENTS 868,080 France Dec. 15, 1941 898,484 France July 3, 1944 634,999 Great Britain Mar. 29, 1950 

